The US "will not look the other way" if the international order is threatened by nations such as China which is trying to restrict navigation or ignore international rules and standards, Hagel warned at the Shangri-La conference in Singapore on Saturday.

He was referring to escalating tensions between Japan and China after Beijing declared an Air Defense Identification Zone over the East China Sea last November.

On Thursday, the United States warned Beijing not to raise regional tension by attempting to interfere with freedom of overflight in international airspace.

The US State Department issued the warning after Japan accused China of “dangerous maneuvers” above territories claimed by the two countries.

Hagel said Washington is opposed to any country's use of intimidation or threat of force to assert territorial claims.

"All nations of the region, including China, have a choice: to unite, and recommit to a stable regional order, or, to walk away from that commitment and risk the peace and security that has benefited millions of people throughout the Asia-Pacific, and billions around the world," he said.

The Pentagon chief also called out China for cyberspying against the US. His remark came less than two weeks after Washington accused five Chinese military officers of hacking into American companies to steal trade secrets.

In response, the Chinese suspended participation in a US-China Cyber Working Group, and issued a report, saying the US is conducting unscrupulous cyber espionage with China as its major target.

Hagel said his country will continue to talk over cyber issues with the Chinese, "because dialogue is essential for reducing the risk of miscalculation and escalation in cyberspace."

MB/MB